Pacing and sensing vectors

ABSTRACT

An apparatus and method for allowing cardiac signals to be sensed and pacing pulse vectors to be delivered between two or more electrodes. In one embodiment, cardiac signals are sensed and pacing pulse vectors are delivered between least one of a first left ventricular electrode and a second left ventricular electrode. Alternatively, cardiac signals are sensed and pacing pulse vectors are delivered between different combinations of the first and second left ventricular electrodes and a first supraventricular electrode. In addition, cardiac signals are sensed and pacing pulse vectors are delivered between different combinations of the first and second left ventricular electrode, the first supraventricular electrode and a conductive housing. In an additional embodiment, a first right ventricular electrode is used to sense cardiac signals and provide pacing pulses with different combinations of the first and second left ventricular electrodes, the first supraventricular electrode and the housing.

TECHNICAL FIELD

[0001] The present invention relates to implantable medical devices, andmore particularly to sensing and delivering energy pulses to and fromthe coronary vasculature.

BACKGROUND

[0002] Cardiac pulse generator systems include a battery powered pulsegenerator and one or more leads for delivering pulses to the heart.Current pulse generators include electronic circuitry for determiningthe nature of an irregular rhythm, commonly referred to as arrhythmia,and for timing the delivery of a pulse for a particular purpose. Thepulse generator is typically implanted into a subcutaneous pocket madein the wall of the chest. Insulated wires called leads attached to thepulse generator are routed subcutaneously from the pocket to theshoulder or neck where the leads enter a major vein, usually thesubclavian vein. The leads are then routed into the site of pacing,usually a chamber of the heart. The leads are electrically connected tothe pulse generators on one end and are electrically connected to theheart on the other end. Electrodes on the leads provide the electricalconnection of the lead to the heart. The leads are used to sense cardiacsignals from the heart and to deliver electrical discharges from thepulse generator to the heart.

[0003] The electrodes are typically arranged on a lead body in two waysor categories. A pair of electrodes which form a single electricalcircuit (i.e., one electrode is positive and one electrode is negative)positioned within the heart is a bipolar arrangement. The bipolararrangement of electrodes requires two insulated wires positioned withinthe lead. When one electrode is positioned in or about the heart on alead and represents one pole and the other electrode representing theother pole is the pulse generator housing, this arrangement is known asa unipolar arrangement. The unipolar arrangement of electrodes requiresone insulated wire positioned within the lead.

[0004] In general, the heart can be divided into two sides, a right sideand a left side. Each side serves a specific function. The right side ofthe heart receives blood from the body and pumps it into the lungs toexchange gases. The left side of the heart receives the oxygenated bloodfrom the lungs and pumps it to the brain and throughout the body.

[0005] Typically, pacing and defibrillation leads are positioned withinthe right chambers of the heart, or positioned within the coronaryvasculature so as to position one or more electrodes adjacent a leftventricular region of the heart. From their positions within or adjacentto the ventricular chambers, the electrodes on the leads are used tosense cardiac signals and to deliver energy pulses in either a bipolaror a unipolar fashion. This sensing and pacing, however, is accomplishedonly within or across the chamber in which the lead is implanted. Thus,there exists a need in the art for providing additional options insensing and delivering electrical energy pulses to a patient's heart.

SUMMARY

[0006] The present subject matter provides for an apparatus and methodfor allowing cardiac signals to be sensed and pacing pulse vectors to beprogrammed for being delivered between two or more electrodes. In oneembodiment, the present subject matter allows for cardiac signals to besensed and pacing pulse vectors to be delivered between at least one ofa first left ventricular electrode and a second left ventricularelectrode in a left ventricular region. In an additional embodiment,cardiac signals are sensed and pacing pulse vectors are deliveredbetween different combinations of the first and/or second leftventricular electrodes in a left ventricular region and a firstsupraventricular electrode in a right atrial region. In addition,cardiac signals are sensed and pacing pulse vectors are deliveredbetween different combinations of the first and/or second leftventricular electrodes in a left ventricular region and a rightventricular electrode in a right ventricular region. In addition, thehousing of the apparatus is conductive so as to allow cardiac signals tobe sensed and pacing pulse vectors to be delivered between differentcombinations of the first and second left ventricular electrodes, thefirst supraventricular electrode, the right ventricular electrode andthe housing.

[0007] In one embodiment, the apparatus includes an implantable pulsegenerator to which is attached a first lead and a second lead. The firstlead includes a first supraventricular electrode adapted to bepositioned in a right atrial region, and the second lead includes thefirst and second left ventricular electrodes that are both adapted to bepositioned adjacent a left ventricular region. The electrodes on thefirst and second leads are coupled to the implantable pulse generatorand to control circuitry within the implantable pulse generator. In oneembodiment, the control circuitry includes a pacing output circuit thatis programmable to control delivery of pacing pulses betweencombinations of the first and/or second left ventricular electrodes inthe left ventricular region and the first supraventricular electrode inthe right atrial region. In an additional embodiment, the pacing outputcircuit is programmable to control delivery of pacing pulses betweencombinations of the first and/or second left ventricular electrodes inthe left ventricular region and the right ventricular electrode in theright ventricular region.

[0008] Examples of the pacing vectors include delivering pacing pulsesfrom the first left ventricular electrode as a cathode to the firstsupraventricular electrode as an anode. Alternatively, pacing pulses aredelivered from the first and/or second left ventricular electrode as acathode to the right ventricular electrode as an anode. In addition, thepacing output circuit delivers the pacing pulse between the first leftventricular electrode and the second left ventricular electrode in aleft ventricular region and the first supraventricular electrode. Inaddition, the control circuitry includes an extended bipolar crosschamber sensor that receives a cardiac signal sensed between the firstleft ventricular electrode and the first supraventricular electrode.Alternatively, the cardiac signal is sensed between the second leftventricular electrode and the first supraventricular electrode. Cardiacsignals sensed between other combinations of the electrodes, includingelectrodes in the right ventricle, are also possible.

[0009] In one embodiment, the first lead further includes a rightventricular electrode adapted to be positioned in a right ventricularregion. Cardiac signals are sensed and pacing pulse vectors aredelivered from various combinations of the right ventricular electrode,the first supraventricular electrode, the first and second leftventricular electrodes and the housing. For example, the controlcircuitry directs the pacing output circuit to deliver pacing pulsesfrom the first left atrial electrode as an anode to the rightventricular electrode as a cathode. Alternatively, the pacing outputcircuit controls delivery of pacing pulses between the first leftventricular electrode, or the second left ventricular electrode and theconductive housing. In an additional embodiment, the pacing outputcircuit controls delivery of pacing pulses between the first leftventricular electrode and the second left ventricular electrode and theright ventricular electrode, where the first and second left ventricularelectrodes are common. Alternatively, the pacing output circuit controlsdelivery of pacing pulses between the first left ventricular electrodeand the second left ventricular electrode and the right ventricularelectrode and the housing of the implantable pulse generator, where thefirst and second left ventricular electrodes are common and the rightventricular electrode and the housing are common. In addition, thecontrol circuitry allows for a cardiac signal to be sensed between oneof the first and second electrodes and the right ventricular electrodeand for pacing pulses to be delivered between one, or both, of the firstand second electrodes and the right ventricular electrode.

[0010] Other combinations of sensing and pacing vectors are possible, aswill be more fully described below.

BRIEF DESCRIPTION OF THE FIGURES

[0011]FIG. 1 is one embodiment of an apparatus according to the presentsubject matter that is implanted into a heart, from which segments havebeen removed to show detail;

[0012]FIG. 2 is one embodiment of an apparatus according to the presentsubject matter that is implanted into a heart, from which segments havebeen removed to show detail;

[0013]FIG. 3 is a block diagram of electronic control circuitry for oneembodiment of an apparatus according to the present subject matter;

[0014]FIG. 4 is one embodiment of an apparatus according to the presentsubject matter that is implanted into a heart, from which segments havebeen removed to show detail;

[0015]FIG. 5 is one embodiment of an apparatus according to the presentsubject matter that is implanted into a heart, from which segments havebeen removed to show detail;

[0016]FIG. 6 is a flow chart of a method according to one embodiment ofthe present subject matter;

[0017]FIG. 7 is a flow chart of a method according to one embodiment ofthe present subject matter;

[0018]FIG. 8 is a flow chart of a method according to one embodiment ofthe present subject matter;

[0019]FIG. 9 is a flow chart of a method according to one embodiment ofthe present subject matter; and

[0020]FIG. 10 is a block diagram of electronic control circuitry for oneembodiment of an apparatus according to the present subject matter.

DETAILED DESCRIPTION

[0021] In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that structuralchanges may be made without departing from the scope of the presentinvention. Therefore, the following detailed description is not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

[0022] Traditional pacemakers allow for pacing and sensing vectors fromwithin single cardiac chambers. These vectors are typically referred toas “unipolar” and “biopolar”, depending upon the relative proximity ofthe electrodes being used in the pacing and/or sensing. Unipolar and/orbiopolar sensing and pacing can be performed within either the atrialchambers or the ventricular chambers of the heart.

[0023]FIG. 1 provides an illustration of unipolar and bipolar pacing andsensing vectors. In FIG. 1, there is shown an implantable pulsegenerator 100 coupled to a first cardiac lead 104 and a second cardiaclead 108. Each of the first cardiac lead 104 and the second cardiac lead108 includes a proximal end (110 for the first lead 104 and 112 for thesecond lead 108) and a distal end (114 for the first lead 104 and 116for the second lead 108). The first lead 104 further includes rightventricular electrodes that include a first right ventricular electrode118 and a second right ventricular electrode 120. The first electrode118 is shown positioned at the distal end 114 (at the tip of the lead)and the second electrode 120 is spaced proximal the first electrode 118to allow for both electrodes to be positioned in the right ventricle122. The second lead 108 further includes a first atrial sensing/pacingelectrode 126 and a second atrial sensing/pacing electrode 128. Thefirst electrode 126 is shown positioned at the distal end 116 (at thetip of the lead) and the second electrode 128 is spaced proximal thefirst electrode 126 to allow for both electrodes to be positioned in theright atrium 130. The cardiac leads 104 and 108 further includeinsulated conductors that extend between each of the electrodes andconnectors at the proximal ends 110 and 112 of the first and secondleads 104 and 108. The connectors allow each of the electrodes (118,120, 126 and 128) to be coupled to electronic control circuitry withinthe implantable pulse generator 100.

[0024] The electronic control circuitry is used to sense cardiac signalsand to deliver pacing pulses through the electrodes. A bipolar vectorfor a chamber is only available when a lead with at least two electrodesis implanted in, or near, a chamber of the heart. In FIG. 1, each of thefirst lead 104 and the second lead 108 are shown with at least twoelectrodes implanted within a chamber of the heart. With respect to thefirst lead 104, the electronic control circuitry is used to sense and/orpace either in a unipolar or a bipolar mode. Vector line 134 indicateseither a unipolar pacing pulse or a unipolar cardiac signal between oneof the first or second electrodes 118 or 120 and the housing 136 of theimplantable medical device 100. In an alternative embodiment, vectorline 138 indicates a bipolar pacing pulse or a bipolar cardiac signalsensed between the first and second electrodes 118 and 120 on the firstlead 104.

[0025] With respect to the second lead 108, the electronic controlcircuitry is used to sense and/or pace either in a unipolar or a bipolarmode. Vector line 140 indicates either a unipolar pacing pulse or aunipolar cardiac signal between one of the first or second electrodes126 or 128 and the housing 136 of the implantable medical device 100. Inan alternative embodiment, vector line 144 indicates a bipolar pacingpulse or a bipolar cardiac signal sensed between the first and secondelectrodes 126 and 128 on the second lead 108. Different combinations ofunipolar and bipolar sensing and pacing from each of the first lead 104and the second lead 108 are programmed into the electronic controlcircuitry through the use of a medical device programmer 150.

[0026] In addition to the sensing and pacing vectors described above, ithas been found that additional sensing and pacing vectors within and/orbetween cardiac chambers have benefits to providing treatment to apatient. In one embodiment, the present subject matter allows foradditional sensing and/or pacing vectors between (e.g., left ventricularchamber and right ventricular chamber, left ventricular chamber andright atrial chamber, left atrial chamber and right atrial chamber) andwithin cardiac chambers when one or more cardiac leads are implanted inthe left atrium and/or left ventricular region in addition to leadsbeing implanted in the right ventricle and/or right atrium.

[0027]FIG. 2 shows one embodiment of an apparatus 200 according to thepresent subject matter. In FIG. 2, the apparatus 200 includes a firstlead 204 and a second lead 226. The first lead 204 has a proximal end205 and a distal end 206 and includes a lead connector 207 having one ormore connector terminals and a lead body 208. In one embodiment,examples of the lead connector 207 and connector terminals include, butare not limited to, LV-1, IS-1 UNI or IS-1 BI. Other lead connectors andconnector terminals are possible. The lead 204 releasably attaches to animplantable pulse generator 210.

[0028] In one embodiment, the lead 204 is adapted to be inserted intoand positioned within the right ventricle 214 and the right atrium 215of the heart 216. The lead 204 includes right ventricular electrodesthat include a first right ventricular electrode 218 and a second rightventricular electrode 219. In one embodiment, the first and second rightventricular electrodes 218 and 219 are adapted to be positioned in theright ventricular region 214. In an additional embodiment, the firstright ventricular electrode 218 is a defibrillation coil electrode andthe second right ventricular electrode 219 is a distal tipsensing/pacing electrode. In addition to the first and second rightventricular electrodes, the first lead 204 further includes additionalelectrodes, such as a first supraventricular electrode 220, where thefirst supraventricular electrode 220 is a defibrillation coil electrode.

[0029] One example of the first lead 204 is an endocardial lead soldunder the trademark ENDOTAK (Cardiac Pacemaker, Inc./ GuidantCorporation, St. Paul, Minn.), which is a tripolar, endocardial leadfeaturing a porous tip electrode. In one embodiment, the tip electrode219 is placed in the apex of the right ventricle and serves as thecathode for intracardiac right ventricular electrogram rate sensing andpacing. Additionally, the two defibrillation coil electrodes serve aseither an anode or a cathode for rate sensing and/or morphology sensingand for defibrillation. The present subject matter, however, uses theelectrodes as either anodes or cathodes depending upon the programmedpacing and sensing vector direction.

[0030] The lead connector 207 electrically connects electrodes 218, 219and 220 via conductors within the lead body 208 to the implantable pulsegenerator 210. The implantable pulse generator 210 contains controlcircuitry that receive cardiac signals sensed with the electrodes andgenerates pacing pulses to be delivered with the electrodes. Theelectronic control circuitry within the implantable pulse generator 210also analyzes and detects certain types of arrhythmias and providespacing pulses, cardioversion and/or defibrillation pulses to correct forthem.

[0031] The apparatus 200 further includes a second lead 226, where thesecond lead 226 has a lead body 230 having a proximal end 232, a distalend 234 and includes a lead connector 235 having one or more connectorterminals. In one embodiment, examples of the lead connector 235 andconnector terminals include, but are not limited to, LV-1, IS-1 UNI orIS-1 BI. Other lead connectors and connector terminals are possible.

[0032] The second lead 226 further includes a first left ventricularelectrode 236 and a second left ventricular electrode 238, where boththe first and second left ventricular electrodes 236 and 238 are adaptedto be positioned adjacent the left ventricle 240 via the coronaryvasculature. In one embodiment, the first and second left ventricularelectrodes 236 and 238 are pacing/sensing electrodes, where the firstelectrode 236 and the second electrode 238 are ring electrodes thateither completely or partially encircles lead body 230. Alternatively,the second electrode 238 is a tip electrode positioned at the distal end234 of the lead 226.

[0033] In one embodiment, the second lead 226 is adapted to be insertedthrough the coronary sinus vein 242 and through the great cardiac vein,or other coronary branch vein, to position the ventricular electrodes236 and 238 adjacent the left ventricle 240 of the heart 216. In analternative embodiment, the second lead 226 is an epicardial lead, wherethe electrodes on the lead 226 are positioned epicardially adjacent theleft ventricle of the heart.

[0034] The lead 226 is releasably attached to the implantable pulsegenerator 210, where the connector terminals couple the ventricularelectrodes 236 and 238 via lead conductors to the electronic controlcircuitry within the implantable pulse generator 210. The controlcircuity within the implantable pulse generator 210 receives cardiacsignals sensed through the use of the electrodes 236 and 238 andgenerates pacing pulses to be delivered through the use of theelectrodes.

[0035] Sensing and pacing with electrodes 218, 219, 220, 236 and 238 andthe housing of the implantable pulse generator 210 is a programmablefeature of the control circuity within the pulse generator 210. In oneembodiment, programming the sensing and pacing vectors is accomplishedthrough the use of a medical device programmer 239. The medical deviceprogrammer 239 is used to program specific pacing and sensing vectorsthat use one or both electrodes 236 and 238 in conjunction withdifferent combinations of electrodes 218, 219, 220 and the housing ofthe implantable pulse generator 210.

[0036] In one embodiment, either of the ventricular electrodes 236 or238 is used in unipolar sensing and pacing between the electrode (236 or238) and the housing 210. Examples of these sensing and pacing vectorsare shown generally at 250. In one example, the control circuity of thepulse generator 210 is programmed to switch from unipolar sensing andpacing between one of the two electrodes 236 or 238 and the housing tounipolar sensing and pacing between the other electrode of 236 or 238and the housing. In an additional embodiment, both ventricularelectrodes 236 and 238 are used in unipolar sensing and pacing betweenthe electrodes 236 and 238 and the housing 210. Alternatively, a bipolarsensing and pacing vector occurs between the two electrodes 236 and 238,where either 236 or 238 is the anode and the other electrode is thecathode.

[0037] In one embodiment, the electrodes 236 and 238 are used in sensingand pacing between the left and right ventricles of the heart. Forexample, one or both of the two electrodes 236 or 238 is used to sensecardiac signals and provide pacing pulses between the electrode(s) 236and/or 238 and the first supraventricular electrode 220. In oneembodiment, this pacing sensing vector is shown generally at 252.Alternatively, one or both of the two electrodes 236 and/or 238 is usedto sense cardiac signals and provide pacing pulses between theelectrode(s) 236 and/or 238 and the first right ventricular electrode218. In one embodiment, this pacing sensing vector is shown generally at254. In addition, one or both of the two electrodes 236 and/or 238 isused to sense cardiac signals and provide pacing pulses between theelectrode(s) 236 and/or 238 and the second right ventricular electrode219. In one embodiment, this pacing sensing vector is shown generally at255. Pacing and sensing vectors 252, 254 and 255 are referred to hereinas “extended” biopolar pacing/sensing vector, as the pacing and sensingoccurs between implanted electrodes across a larger portion of the heartthan is typical with a traditional bipolar pacing/sensing vector.

[0038] In one embodiment, electrodes 218, 219, 220, 236 and 238 arecreated from either platinum, platinum-iridium alloys or alloys whichcan include cobalt, iron, chromium, molybdenum, nickel and/or manganese.In addition, the second right ventricular electrode 219 and the secondleft ventricular electrode 238 are porous electrodes. Alternatively, thesecond right ventricular electrode 219, the first left ventricularelectrode 236, and the second left ventricular electrode 238 are ringelectrodes that either partially or fully encircle their respective leadbodies, 208 or 230, as previously discussed. In addition, the secondright ventricular electrode 219 further includes a helical screw forpositive fixation of the lead 204.

[0039] In one embodiment, the lead bodies 208 and 230 are formed of abiocompatible polymer such as silicone rubber and/or polyurethane. Thelead bodies 208 and 230 further includes one or more lumens which areadapted to receive a stylet, or guidewire, for guiding and implantingthe leads 204 and 226. In one embodiment, the lead bodies 208 and 230include a lumen that extends from an opening at the proximal end of thelead to the distal end of the lead to allow the lead to be controlledthrough the use of the stylet, or guidewire. In one embodiment, thestylet lumen is formed from a lead conductor extending from theconnector terminal and the proximal end of the lead, 204 and 226 to adistal most electrode on the lead (e.g., the second right ventricularelectrode 219 and the second left ventricular electrode 238).

[0040]FIG. 3 shows one embodiment of control circuitry 300, aspreviously mentioned, for an implantable pulse generator 302. In thepresent embodiment, the implantable pulse generator 302 is adapted toreceive the first and second leads (e.g., 204 and 226), as discussed.

[0041] The control circuitry 300 is contained within a hermeticallysealed housing 304. The housing 304 is electrically conductive and actsas a reference electrode in unipolar pacing and sensing, as will bedescribed below. The pulse generator 302 further includes a connectorblock 306 that receives the connector terminals of the cardiac leads,such as 204 and 226. The connector block 306 includes contacts 308, 310,312, 314 and 316 that connect electrodes 220, 218, 219, 238 and 236,respectively, to sense amplifiers 320 and 326.

[0042] In one embodiment, an output from amp 320 is shown coupled to aright ventricular activity sensor 328 to allow for a bipolar cardiacsignal to be sensed from the right ventricle 214 (FIG. 2) between thefirst right ventricular electrode 218 and the second right ventricularelectrode 219 via switch matrix 332. In this embodiment, the extendedbiopolar cross chamber sensing is accomplished by the controller 340configuring the switch matrix 332 such that the left ventricularactivity sensor 334 receives an extended bipolar cardiac signal sensedbetween the second left ventricular electrode 238 and the first rightventricular electrode 218. Alternatively, the left ventricular activitysensor 334 receives the extended bipolar cardiac signal sensed betweenthe first left ventricular electrode 236 and the first right ventricularelectrode 218. The left ventricular activity sensor 334 also receivesextended bipolar cardiac signal sensed between the second leftventricular electrode 238 and the first supraventricular electrode 220,in addition to an extended bipolar cardiac signal sensed between thefirst left ventricular electrode 236 and the first supraventricularelectrode 220. In addition, the left ventricular activity sensor 334receives the extended bipolar cardiac signal sensed between the firstand second left ventricular electrodes 236 and 238 and the first rightventricular electrode 218. Alternatively, the left ventricular activitysensor 334 receives the extended bipolar cardiac signal sensed betweenthe first and second left ventricular electrodes 236 and 238 and thesecond right ventricular electrode 219. Which combination of extendedbipolar cardiac signals are sensed depends upon the sensing vectorsprogrammed into the switch matrix 332 by control circuitry 300. FIG. 3also shows the output from amp 326 coupled to a left ventricularactivity sensor 334 to allow for a bipolar cardiac signal to be sensedfrom the left ventricle 240 (FIG. 2) between the first and second leftventricular electrodes 236 and 238.

[0043] The control circuitry 300 further includes a controller 340,where the controller 340 receives the cardiac signals from the sensingcircuits 328 and 334 and analyzes the cardiac signals to determine whenand if to deliver electrical energy pulses to the heart. In oneembodiment, the controller 340 is a microprocessor, however, othercircuity under the control of software and/or firmware may be used asthe controller 340.

[0044] In one embodiment, the controller 340 implements one or moreanalysis protocols stored in a memory 344 to analyze one or more of thesensed cardiac signals and to provide pacing, cardioversion and/ordefibrillation therapy to one or more chambers of the heart undercertain predetermined conditions. Memory 344 is also used to store oneor more sensed cardiac signals to be downloaded to a medical deviceprogrammer 348 for analysis. In one embodiment, the control circuitry300 communicates with the medical device programmer 348 through areceiver/transmitter 350, where cardiac signals, programs and operatingparameters for the programs for the implantable medical device aretransmitted and received through the use of the programmer 348 and thereceiver/transmitter 350. Power for the control circuitry is supplied bya battery 354.

[0045] The controller 340 further controls a pace output circuit 360 anda defibrillation output circuit 364 to provide pacing, cardioversionand/or defibrillation therapy to one or more chambers of the heart undercertain predetermined conditions. In one embodiment, the pace outputcircuit 360 is coupled to contacts 308, 310, 312, 314 and 316 via switchmatrix 332 to allow for bipolar pacing between electrodes 218 and 219,and extended bipolar pacing between electrodes 236 and/or 238 and 218,219 or 220, as previously described. In an additional, extended bipolarpacing and sensing occurs between electrodes 236 and 238, electricallycoupled in common, and electrode 218, 219 or 220. In one embodiment,electrodes 236 and/or 238 are the cathode and electrodes 218, 219 and/or220 are used as the anode in the extended bipolar pacing and sensing.Alternatively, electrodes 236 and/or 238 are the anode and electrodes218, 219 and/or 220 are used as the cathode in the extended bipolarpacing and sensing. In an additional embodiment, when bipolar pacingoccurs between electrodes 218 and 219, electrode 218 is the cathode andelectrode 219 is the anode.

[0046] In addition to the extended bipolar sensing and pacing, electrode236 and/or 238 are used in conjunction with the conductive housing 304of the implantable pulse generator to allow for unipolar sensing andpacing between either of electrodes 236 or 238 and the housing 304. Inan additional embodiment, the described polarity of the electrodes usedin the bipolar pacing and sensing is reversed to allow for additionaloptions in providing therapy to a patient.

[0047] The different combinations of the pacing and sensing vectors areprogrammable features that are selected and implemented in theimplantable pulse generator 302 through the use of the medical deviceprogrammer 348. Thus, different combinations of pacing and sensingvectors (as described above) are selected and programmed based on eachpatient's specific needs. In addition, the programmable nature of thesensing and pacing vectors described herein allows for one or more ofthe sensing and/or pacing vectors to be altered based on sensed cardiacsignals and the response to the pacing pulses delivered to the patient'sheart.

[0048]FIG. 4 shows an additional embodiment of an apparatus 400according to the present subject matter. In FIG. 4, the apparatus 400includes a first lead 204, as described above for FIG. 2. FIG. 4 furtherincludes a second lead 404, where the second lead 404 includes aplurality of electrodes. In one embodiment, the second lead 404 includesa first left ventricular electrode 408, a second left ventricularelectrode 412 and a third left ventricular electrode 416.

[0049] Lead 404 includes a lead connector 418 having connector terminalsfor coupling the electrodes 408, 412 and 416 via conductors within thelead body to the control circuitry within the implantable pulsegenerator 420. In one embodiment, the electrodes 408, 412 and 416 areadapted to be positioned adjacent the left ventricle 430 via thecoronary vasculature. In one embodiment, the first, second and thirdleft ventricular electrodes 408, 412 and 416 are pacing/sensingelectrodes, where the electrodes are all ring electrodes that eithercompletely or partially encircles lead body, or are a combination ofring electrodes and distal tip electrode positioned at the distal end ofthe lead 404. In addition, the lead body of the lead 404 forms a helixthat is adapted to allow for the electrodes 408, 412 and 416 to bettercontact the cardiac tissue adjacent the left ventricle of the heart.

[0050] In one embodiment, the first and second left ventricularelectrodes 408 and 412 are electrically connected in common, wherepacing and sensing signals occur between combinations of the first andsecond left ventricular electrodes 408 and 412, in common, and the thirdleft ventricular electrode 416. In an alternative embodiment, the firstand second left ventricular electrodes 408 and 412 both have the sameelectrical polarity (e.g., anode or cathode), but are not electricallycoupled in common. Thus, each electrode 408 and 412 is electricallyisolated, but has the same electrical polarity. The control circuitrywithin the implantable pulse generator 420 then controls each electrodefor delivering pacing signals and sensing cardiac signals to the heart.In one embodiment, this allows the control circuity to individuallyadjust the output of one or both the electrodes 408 and 412 based on thepacing threshold of the patient.

[0051] In an additional embodiment, the control circuitry isprogrammable to select and switch between sensing unipolar cardiacsignal and/or delivering unipolar pacing pulses between each electrodes408, 412 or 416 and the housing of the implantable pulse generator 420.Additionally, the control circuitry is also programmable to select andswitch between sensing extended bipolar signals and/or deliveringextended bipolar pacing pulses between each electrodes 408, 412 or 416and either the first right ventricular electrode 218, the second rightventricular electrode 219 or the first supraventricular electrode 220.

[0052]FIG. 5 shows an additional embodiment of an apparatus 500according to the present subject matter. In FIG. 5, the apparatus 500includes the first lead 104, as described above for FIG. 1, and lead226, as described above for FIG. 2. This embodiment allows forcombinations of electrodes 118, 120 of the first lead 104 and electrodes236 and 238 of the second lead 226 to be programmed to sense cardiacsignals and/or deliver pacing pulses between any number of electrodecombinations. For example, extended bipolar cardiac signals are sensedbetween and/or pacing pulses are delivered between electrode 236 andelectrode 118 and/or 120, and/or extended bipolar cardiac signals aresensed between and/or pacing pulses are delivered between electrode 238and electrode 118 and/or 120. The control circuitry of the implantablepulse generator 504 is programmable to select and switch between sensingunipolar cardiac signal and/or delivering unipolar pacing pulses betweeneach electrodes 118, 120, 236 or 238 and the housing of the implantablepulse generator 504. Additionally, the control circuitry is alsoprogrammable to select and switch between sensing unipolar cardiacsignal and/or delivering unipolar pacing pulses between each electrodes236 and 238 and either electrode 118 or 120.

[0053] In an additional embodiment, the connector blocks of any of theimplantable pulse generators described above can further include areference electrode for use in sensing unipolar cardiac signals anddelivering unipolar pacing pulses between any of the aforementionedelectrodes (e.g., 118, 120, 218, 219, 220, 236, 238, 408, 412 or 416).An example of the connector block electrode is shown in FIG. 5 at 510.

[0054]FIG. 6 shows one embodiment of a method 600 according to oneaspect of the present subject matter. At 610, a first cardiac leadhaving at least a first supraventricular electrode is implanted within aheart. In one embodiment, the first supraventricular electrode ispositioned within the right atrium of the heart and/or a major veinleading to the right atrium. At 620, a second cardiac lead having atleast a first left ventricular electrode and a second left ventricularelectrode is implanted within a heart. In one embodiment, the first andsecond left ventricular electrodes are positioned in a left ventricularregion of the heart.

[0055] Specific examples of the first supraventricular electrode and thefirst and second left ventricular electrodes were presented above. Theseexamples, however, are not intended to be limiting and differentexamples of the first supraventricular electrode and the first andsecond left ventricular electrodes are possible. These additionalexamples include, but are not limited to, the first supraventricularelectrode taking the form of a pacing/sensing electrode, such as a ringelectrode. Additionally, one or both of the left ventricular electrodescan take the form of a coil electrode that can be used in conjunctionwith any of the aforementioned structures for the first supraventricularor ventricular electrodes.

[0056] At 630, pacing pulse vectors and sensing vectors are programmedbetween one or more of the first left ventricular electrode and thesecond left ventricular electrode, and the first supraventricularelectrode in the right atrial region. At 640, pacing pulses aredelivered between the first and/or second left ventricular electrode inthe left ventricular region and the first supraventricular electrode inthe right atrial region, according to the programmed pacing pulsevectors. In one embodiment, the first and/or second left ventricularelectrode is used as the cathode, while the first supraventricularelectrode is used as the anode. In an alternative embodiment, the firstsupraventricular electrode is used as the cathode, while the firstand/or the second left ventricular electrode is used as the anode.

[0057] In addition to providing pacing pulses between the first and/orsecond left ventricular electrode and the first supraventricularelectrode, sensing vectors between the first left ventricular electrodeand/or the second left ventricular electrode, and the firstsupraventricular electrode are sensed at 650 according to the programmedsensing vector. In one embodiment, the cardiac signal is sensed wherethe first and/or second left ventricular electrode is an anode and thefirst supraventricular electrode is a cathode. In an alternativeembodiment, the cardiac signal is sensed where the firstsupraventricular electrode is an anode and the first and/or second leftventricular electrode is a cathode. In an additional embodiment, thehousing of an implantable pulse generator is conductive and is used inan electrode in common with the first supraventricular electrode, aspreviously discussed.

[0058]FIG. 7 shows one embodiment of a method 700 according to oneaspect of the present subject matter. At 710, a first cardiac leadhaving at least a right ventricular electrode is implanted within aheart. In one embodiment, the right ventricular electrode is either adefibrillation electrode, such as the first right ventricular electrode218, or a pace/sense electrode, such as the second right ventricularelectrode 219. These examples, however, are not intended to be limitingand different examples of the right ventricular electrode are possible.In one embodiment, the right ventricular electrode is positioned withinthe right ventricle of the heart.

[0059] At 720, a second cardiac lead having at least a first leftventricular electrode and a second left ventricular electrode isimplanted within a heart. In one embodiment, the first and second leftventricular electrodes are positioned in a left ventricular region ofthe heart. In one embodiment, the first and second left ventricularelectrodes are as previously described. These examples, however, are notintended to be limiting and different examples of the first and secondleft ventricular electrodes are possible. For example, one or both ofthe left ventricular electrodes can take the form of a coil electrodethat can be used in conjunction with any of the aforementionedstructures for the supraventricular or ventricular electrodes.

[0060] At 730, pacing pulse vectors and sensing vectors are programmedbetween one or more of the first and second left ventricular electrodes,and the right ventricular electrode. At 740, pacing pulses are deliveredbetween the first and/or second left ventricular electrode and the rightventricular electrode, according to the programmed pacing pulse vectors.In one embodiment, the first and/or second left ventricular electrode isused as the cathode, while the right ventricular electrode is used asthe anode. In an alternative embodiment, the right ventricular electrodeis used as the cathode, while the first and/or the second leftventricular electrode is used as the anode.

[0061] In addition to providing pacing pulses between the first and/orsecond left ventricular electrode and the right ventricular electrode,sensing vectors between one, or both, of the first and second leftventricular electrodes and the right ventricular electrode are sensed at750 according to the programmed sensing vector. In one embodiment, thecardiac signal is sensed where the first and/or second left ventricularelectrode is an anode and the right ventricular electrode is a cathode.In an alternative embodiment, the cardiac signal is sensed where theright ventricular electrode is an anode and the first and/or second leftventricular electrode is a cathode. In an additional embodiment, thehousing of an implantable pulse generator is conductive and is used inan electrode in common with the right ventricular electrode, aspreviously discussed.

[0062]FIG. 8 shows one embodiment of a method 800 according to oneaspect of the present subject matter. At 810, a first cardiac leadhaving at least a first supraventricular electrode and a firstventricular electrode is implanted within a heart. In one embodiment,the first supraventricular electrode is positioned within the rightatrium of the heart, while the first ventricular electrode is positionedwithin the right ventricle of the heart. In one embodiment, the rightventricular electrode is either a defibrillation electrode, such as thefirst right ventricular electrode 218, or a pace/sense electrode, suchas the second right ventricular electrode 219. These examples, however,are not intended to be limiting and different examples of the rightventricular electrode are possible. At 820, a second cardiac lead havingat least a first left ventricular electrode and a second leftventricular electrode is implanted within a heart. In one embodiment,the first and second left ventricular electrodes are positioned in aleft ventricular region of the heart.

[0063] Specific examples of the first supraventricular and ventricularelectrodes and the first and second left ventricular electrodes werepresented above. These examples, however, are not intended to belimiting and different examples of the first supraventricular andventricular electrodes and the first and second left ventricularelectrodes are possible. These additional examples include, but are notlimited to, the first supraventricular or ventricular electrode takingthe form of a pacing/sensing electrode, such as a ring electrode.Additionally, one or both of the left ventricular electrodes can takethe form of a coil electrode that can be used in conjunction with any ofthe aforementioned structures for the first supraventricular orventricular electrodes.

[0064] At 830, pacing pulse vectors and sensing vectors are programmedbetween one or more of the first left ventricular electrode and/or thesecond left ventricular electrode, and the first supraventricularelectrode in the right atrial region and the right ventricular electrodein the right ventricle. At 840, pacing pulses are delivered betweeneither the first and/or second left ventricular electrode and the firstsupraventricular electrode and/or the first right ventricular electrode,according to the programmed pacing pulse vectors. In one embodiment, thefirst and/or second left ventricular electrode is used as the cathode,while the first supraventricular and/or the right ventricular electrodeis used as the anode. In an alternative embodiment, the firstsupraventricular and/or right ventricular electrode is used as thecathode, while the first and/or the second left ventricular electrode isused as the anode.

[0065] In addition to providing pacing pulses between the first and/orsecond left ventricular electrode and the first supraventricularelectrode and/or right ventricular electrode, sensing vectors betweenone or both of the first and/or second left ventricular electrodes, andthe first supraventricular and/or the right ventricular electrode aresensed at 850 according to the programmed sensing vector. In oneembodiment, the cardiac signal is sensed where the first and/or secondleft ventricular electrode is an anode and the first supraventricularelectrode and/or the right ventricular electrode is a cathode. In analternative embodiment, the cardiac signal is sensed where the firstsupraventricular electrode and/or the right ventricular electrode is ananode and the first and/or second left ventricular electrode is acathode. In an additional embodiment, the housing of an implantablepulse generator is electrically conductive and used as an electrode incommon with the first supraventricular electrode and/or the rightventricular electrode, as previously discussed.

[0066]FIG. 9 shows one embodiment of a method 900 according to anadditional aspect of the present subject matter. At 910, a first cardiaclead having at least a first right ventricular electrode and a secondright ventricular electrode is implanted within a heart. In oneembodiment, the first and second right ventricular electrodes arepositioned within the right ventricle of the heart. Specific examples ofthe first and second right ventricular electrodes were presented above,where the first right ventricular electrode is a defibrillation coilelectrode positioned in a right ventricular region, and the second rightventricular electrode is a pacing/sensing electrode located at or nearthe distal tip of the lead and positioned in an apex of the rightventricular region. At 920, a pacing level pulse is delivered from afirst ventricular defibrillation electrode as a cathode to a firstventricular pacing/sensing electrode as an anode.

[0067]FIG. 10 shows an additional embodiment of control circuitry 1000,as previously mentioned, for an implantable pulse generator 1002. In thepresent embodiment, the implantable pulse generator 1002 is adapted toreceive the first and second leads (e.g., 204 and 226, 204 and 404, 104and 226), as previously discussed.

[0068] The control circuitry 1000 is contained within a hermeticallysealed housing 1004. The housing 1004 is electrically conductive andacts as a reference electrode in unipolar pacing and sensing, as will bedescribed below. The pulse generator 1002 further includes a connectorblock 1006 that receives the connector terminals of the cardiac leads,such as 204 and 226, 204 and 404, or 104 and 226. In one embodiment, theconnector block 1006 includes contacts 1008, 1010, 1012, 1014 and 1016that connect electrodes 220, 218, 219, 238 and 236, respectively, tosense amplifiers 1020, 1022, 1024 and 1026.

[0069] In one embodiment, an output from amp 1020 is shown coupled to aright ventricular activity sensor 1028 to allow for a bipolar cardiacsignal to be sensed from the right ventricle 214 (FIG. 2) between thefirst right ventricular electrode 218 and the second right ventricularelectrode 219. In addition, an output from amps 1022 and 1024 is showncoupled to an extended bipolar cross chamber sensor 1030. In thisembodiment, the extended biopolar cross chamber sensor 1030 receives anextended bipolar cardiac signal sensed between the second leftventricular electrode 238 and the first right ventricular electrode 218.Alternatively, the extended biopolar cross chamber sensor 1030 receivesthe extended bipolar cardiac signal sensed between the first leftventricular electrode 236 and the first right ventricular electrode 218.The extended bipolar cross chamber sensor 1030 also receives extendedbipolar cardiac signal sensed between the second left ventricularelectrode 238 and the first supraventricular electrode 220, in additionto an extended bipolar cardiac signal sensed between the first leftventricular electrode 236 and the first supraventricular electrode 220.In addition, the extended biopolar cross chamber sensor 1030 receivesthe extended bipolar cardiac signal sensed between the first and secondleft ventricular electrodes 236 and 238 and the first right ventricularelectrode 218. Alternatively, the extended biopolar cross chamber sensor1030 receives the extended bipolar cardiac signal sensed between thefirst and second left ventricular electrodes 236 and 238 and the secondright ventricular electrode 219. Which combination of extended bipolarcardiac signals are sensed depends upon the sensing vectors programmedinto the control circuitry 1000. FIG. 10 also shows an output from amp1026 coupled to a left ventricular activity sensor 1034 to allow for abipolar cardiac signal to be sensed from the left ventricle 240 (FIG. 2)between the first and second left ventricular electrodes 236 and 238.

[0070] The control circuitry 1000 farther includes a controller 1040,where the controller 1040 receives the cardiac signals from the sensingcircuits 1028, 1030 and 1034 and analyzes the cardiac signals todetermine when and if to deliver electrical energy pulses to the heart.In one embodiment, the controller 1040 is a microprocessor, however,other circuity under the control of software and/or firmware may be usedas the controller 1040.

[0071] In one embodiment, the controller 1040 implements one or moreanalysis protocols stored in a memory 1044 to analyze one or more of thesensed cardiac signals and to provide pacing, cardioversion and/ordefibrillation therapy to one or more chambers of the heart undercertain predetermined conditions. Memory 1044 is also used to store oneor more sensed cardiac signals to be downloaded to a medical deviceprogrammer 1048 for analysis. In one embodiment, the control circuitry1000 communicates with the medical device programmer 1048 through areceiver/transmitter 1050, where cardiac signals, programs and operatingparameters for the programs for the implantable medical device aretransmitted and received through the use of the programmer 1048 and thereceiver/transmitter 1050. Power for the control circuitry is suppliedby a battery 1054.

[0072] The controller 1040 further controls a pace output circuit 1060and a defibrillation output circuit 1064 to provide pacing,cardioversion and/or defibrillation therapy to one or more chambers ofthe heart under certain predetermined conditions. In one embodiment, thepace output circuit 1060 is coupled to contacts 1008, 1010, 1012, 1014and 1016 to allow for bipolar pacing between electrodes 218 and 219, andextended bipolar pacing between electrodes 236 and/or 238 and 218, 219or 220, as previously described. In an additional, extended bipolarpacing and sensing occurs between electrodes 236 and 238, electricallycoupled in common, and electrode 218, 219 or 220. In one embodiment,electrodes 236 and/or 238 are the cathode and electrodes 218, 219 and/or220 are used as the anode in the extended bipolar pacing and sensing.Alternatively, electrodes 236 and/or 238 are the anode and electrodes218, 219 and/or 220 are used as the cathode in the extended bipolarpacing and sensing. In an additional embodiment, when bipolar pacingoccurs between electrodes 218 and 219, electrode 218 is the cathode andelectrode 219 is the anode.

[0073] In addition to the extended bipolar sensing and pacing, electrode236 and/or 238 are used in conjunction with the conductive housing 1004of the implantable pulse generator to allow for unipolar sensing andpacing between either of electrodes 236 or 238 and the housing 1004. Inan additional embodiment, the described polarity of the electrodes usedin the bipolar pacing and sensing is reversed to allow for additionaloptions in providing therapy to a patient.

[0074] The different combinations of the pacing and sensing vectors areprogrammable features that are selected and implemented in theimplantable pulse generator 1002 through the use of the medical deviceprogrammer 1048. Thus, different combinations of pacing and sensingvectors (as described above) are selected and programmed based on eachpatient's specific needs. In addition, the programmable nature of thesensing and pacing vectors described herein allows for one or more ofthe sensing and/or pacing vectors to be altered based on sensed cardiacsignals and the response to the pacing pulses delivered to the patient'sheart.

[0075] In addition to the apparatus and methods described for providingpacing and sensing across ventricular regions of the heart, the presentsubject matter can also be used in a system having electrodes implantedin and around the supraventricular region of the heart. So, the presentsubject matter could be used to sense and pace bipolarly across theright and left atrium of the heart.

[0076] In addition to the apparatus and methods for providing pacing andsensing across the regions of the heart using two left ventricularelectrodes, the present subject matter can also use a cardiac leadhaving a plurality of left ventricular electrodes, such as those shownand described in the example of FIG. 4.

[0077] It is to be understood that the above description is intended tobe illustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. It should be noted that embodiments discussed indifferent portions of the description or referred to in differentdrawings can be combined to form additional embodiments of the presentinvention. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. An apparatus, comprising: a first lead, where thefirst lead includes a right ventricular electrode adapted to bepositioned in a right ventricular region; a second lead, where thesecond lead includes a first left ventricular electrode and a secondleft ventricular electrode, the first and second ventricular electrodesadapted to be positioned adjacent a left ventricular region; animplantable pulse generator, where the first lead and the second leadare coupled to the implantable pulse generator and where the first andsecond left ventricular electrodes and the right ventricular electrodeare coupled to control circuitry within the implantable pulse generator,and wherein the control circuitry includes a pacing output circuit thatis programmable to control delivery of pacing pulses betweencombinations of the first and second left ventricular electrodes in theleft ventricular region and the right ventricular electrode in the rightventricular region.
 2. The apparatus of claim 1, wherein the first leftventricular electrode and the second left ventricular electrode arepacing/sensing electrodes, and the right ventricular electrode is adefibrillation coil electrode.
 3. The apparatus of claim 1, wherein thefirst left ventricular electrode, the second left ventricular electrodeand the right ventricular electrode are pacing/sensing electrodes. 4.The apparatus of claim 1, wherein the second lead includes a third leftventricular electrode, where the third left ventricular electrode isadapted to be positioned adjacent to the left ventricular region.
 5. Theapparatus of claim 4, wherein the control circuitry is programmable tocontrol delivery of pacing pulses between combinations of the first leftventricular electrode, the second left ventricular electrode, the thirdleft ventricular electrode and the right ventricular electrode.
 6. Theapparatus of claim 4, wherein the control circuitry includes a rightventricular activity sensor, a left ventricular activity sensor and aswitch matrix coupled to both the right ventricular activity sensor andthe left ventricular activity sensor, where the control circuitryconfigures the switch matrix to receive an extended bipolar cardiacsignal sensed between one or more of the first, second or third leftventricular electrode and the first right ventricular electrode.
 7. Theapparatus of claim 4, wherein the implantable pulse generator includes aconductive housing, where the control circuitry is programmable tocontrol delivery of pacing pulses between combinations of the first leftventricular electrode, the second left ventricular electrode, the thirdleft ventricular electrode and the conductive housing.
 8. The apparatusof claim 1, wherein the control circuitry includes a right ventricularactivity sensor, a left ventricular activity sensor and a switch matrixcoupled to both the right ventricular activity sensor and the leftventricular activity sensor, where the control circuitry configures theswitch matrix to receive an extended bipolar cardiac signal sensedbetween one or more of the first and second electrode and the firstright ventricular electrode.
 9. The apparatus of claim 1, wherein thecontrol circuitry directs the pacing output circuit to deliver pacingpulses between the first left ventricular electrode, the second leftventricular electrode and the right ventricular electrode.
 10. Theapparatus of claim 1, wherein the first lead further includes a firstsupraventricular electrode adapted to be positioned in a right atrialregion, and where the control circuitry directs the pacing outputcircuit to deliver pacing pulses between the first left ventricularelectrode, the second left ventricular and the first supraventricularelectrode.
 11. The apparatus of claim 10, wherein the implantable pulsegenerator includes a conductive housing, where the pacing output circuitcontrols delivery of pacing pulses between the first left ventricularelectrode, the second left ventricular electrode, the firstsupraventricular electrode and the housing, where the first and secondleft ventricular electrodes are common and the first supraventricularelectrode and the housing are common.
 12. The apparatus of claim 1,wherein the implantable pulse generator includes a conductive housing,where the pacing output circuit controls delivery of pacing pulsesbetween the first left ventricular electrode and the conductive housing.13. The apparatus of claim 1, wherein the implantable pulse generatorincludes a conductive housing, where the pacing output circuit controlsdelivery of pacing pulses between the second left ventricular electrodeand the conductive housing.
 14. An apparatus, comprising: a first lead,where the first lead includes a first supraventricular electrode adaptedto be positioned in a right atrial region; a second lead, where thesecond lead includes a first left ventricular electrode and a secondleft ventricular electrode, the first and second ventricular electrodesadapted to be positioned adjacent a left ventricular region; animplantable pulse generator, where the first lead and the second leadare coupled to the implantable pulse generator and where the first andsecond left ventricular electrodes and the first supraventricularelectrode are coupled to control circuitry within the implantable pulsegenerator, and wherein the control circuitry includes a pacing outputcircuit that is programmable to control delivery of pacing pulsesbetween combinations of the first and second left ventricular electrodesin the left ventricular region and the first supraventricular electrodein the right atrial region.
 15. The apparatus of claim 14, wherein thefirst left ventricular electrode and the second left ventricularelectrode are pacing/sensing electrodes and the first supraventricularelectrode is a defibrillation coil electrode.
 16. The apparatus of claim14, wherein the second lead includes a third left ventricular electrode,where the third left ventricular electrode is adapted to be positionedadjacent the left ventricular region.
 17. The apparatus of claim 16,wherein the control circuitry is programmable to control delivery ofpacing pulses between combinations of the first left ventricularelectrode, the second left ventricular electrode, the third leftventricular electrode and the right ventricular electrode.
 18. Theapparatus of claim 16, wherein the control circuitry includes a rightventricular activity sensor, a left ventricular activity sensor and aswitch matrix coupled to both the right ventricular activity sensor andthe left ventricular activity sensor, where the control circuitryconfigures the switch matrix to receive an extended bipolar cardiacsignal sensed between one or more of the first and second leftventricular electrodes and the first supraventricular electrode.
 19. Theapparatus of claim 14, wherein the control circuitry includes a rightventricular activity sensor, a left ventricular activity sensor and aswitch matrix coupled to both the right ventricular activity sensor andthe left ventricular activity sensor, where the control circuitryconfigures the switch matrix to receive an extended bipolar cardiacsignal sensed between the first left ventricular electrode and the firstsupraventricular electrode.
 20. The apparatus of claim 14, wherein thecontrol circuitry includes a right ventricular activity sensor, a leftventricular activity sensor and a switch matrix coupled to both theright ventricular activity sensor and the left ventricular activitysensor, where the control circuitry configures the switch matrix toreceive an extended bipolar cardiac signal sensed between the secondleft ventricular electrode and the first supraventricular electrode. 21.The apparatus of claim 14, wherein the control circuitry includes aright ventricular activity sensor, a left ventricular activity sensorand a switch matrix coupled to both the right ventricular activitysensor and the left ventricular activity sensor, where the controlcircuitry configures the switch matrix to receive an extended bipolarcardiac signal sensed between the first and second left ventricularelectrodes and the first supraventricular electrode.
 22. The apparatusof claim 14, wherein the control circuitry directs the pacing outputcircuit to deliver pacing pulses between the first left ventricularelectrode and the first supraventricular electrode.
 23. The apparatus ofclaim 14, wherein the first lead further includes a first rightventricular electrode adapted to be positioned in a right ventricularregion, and where the control circuitry directs the pacing outputcircuit to deliver pacing pulses between the first left ventricularelectrode and the first right ventricular electrode.
 24. The apparatusof claim 14, wherein the control circuitry directs the pacing outputcircuit to deliver pacing pulses between the second left ventricularelectrode and the first left ventricular electrode.
 25. The apparatus ofclaim 14, wherein the pacing output circuit delivers the pacing pulsebetween the first left ventricular electrode and the second leftventricular electrode in a left ventricular region and the firstsupraventricular electrode.
 26. The apparatus of claim 14, wherein theimplantable pulse generator includes a conductive housing, where thepacing output circuit controls delivery of pacing pulses between thefirst left ventricular electrode and the conductive housing.
 27. Theapparatus of claim 14, wherein the implantable pulse generator includesa conductive housing, where the pacing output circuit controls deliveryof pacing pulses between the second left ventricular electrode and theconductive housing.
 28. The apparatus of claim 27, wherein the firstlead further includes a right ventricular electrode adapted to bepositioned in a right ventricular region, and where the pacing outputcircuit controls delivery of pacing pulses between the first leftventricular electrode and the second left ventricular electrode and theright ventricular electrode and the housing of the implantable pulsegenerator, where the first and second left ventricular electrodes arecommon and the right ventricular electrode and the housing are common.29. The apparatus of claim 14, wherein the first lead includes a rightventricular electrode adapted to be positioned in a right ventricularregion, and wherein the control circuitry allows for a cardiac signal tobe sensed between one of the first and second electrodes and the rightventricular electrode and for pacing pulses to be delivered between bothof the first and second electrodes and the first right ventricularelectrode.
 30. An apparatus, comprising: a lead, where the lead includesa first left ventricular electrode and a second left ventricularelectrode, the first and second ventricular electrodes adapted to bepositioned adjacent a left ventricular region; an implantable pulsegenerator, where the lead is coupled to the implantable pulse generatorand where the first and second left ventricular electrodes are coupledto control circuitry within the implantable pulse generator, and whereinthe implantable pulse generator includes a conductive housing couple tothe control circuitry, the control circuitry including a pacing outputcircuit that is programmable to control delivery of pacing pulsesbetween combinations of the first and second left ventricular electrodesin the left ventricular region and the conductive housing of theimplantable pulse generator.
 31. The apparatus of claim 30, wherein thecontrol circuitry includes a right ventricular activity sensor, a leftventricular activity sensor and a switch matrix coupled to both theright ventricular activity sensor and the left ventricular activitysensor, where the control circuitry configures the switch matrix toreceive an extended bipolar cardiac signal sensed between the first leftventricular electrode and the conductive housing.
 32. The apparatus ofclaim 30, wherein the control circuitry includes a right ventricularactivity sensor, a left ventricular activity sensor and a switch matrixcoupled to both the right ventricular activity sensor and the leftventricular activity sensor, where the control circuitry configures theswitch matrix to receive an extended bipolar cardiac signal sensedbetween the second left ventricular electrode and the conductivehousing.
 33. The apparatus of claim 32, wherein the control circuitryincludes a right ventricular activity sensor, a left ventricularactivity sensor and a switch matrix coupled to both the rightventricular activity sensor and the left ventricular activity sensor,where the control circuitry configures the switch matrix to receive anextended bipolar cardiac signal sensed between the first and second leftventricular electrodes and the conductive housing.
 34. The apparatus ofclaim 30, wherein the lead includes a third left ventricular electrode,where the third left ventricular electrode is adapted to be positionedadjacent the left ventricular region.
 35. The apparatus of claim 34,wherein the control circuitry is programmable to control delivery ofpacing pulses between combinations of the first left ventricularelectrode, the second left ventricular electrode, the third leftventricular electrode and the right ventricular electrode.
 36. Theapparatus of claim 34, wherein the control circuitry includes a rightventricular activity sensor, a left ventricular activity sensor and aswitch matrix coupled to both the right ventricular activity sensor andthe left ventricular activity sensor, where the control circuitryconfigures the switch matrix to receive an extended bipolar cardiacsignal sensed between one or more of the first, second and third leftventricular electrodes and the conductive housing.
 37. The apparatus ofclaim 30, wherein the pacing output circuit controls delivery of pacingpulses between the first left ventricular electrode and the conductivehousing.
 38. The apparatus of claim 30, wherein the pacing outputcircuit controls delivery of pacing pulses between the second leftventricular electrode and the conductive housing.
 39. The apparatus ofclaim 38, wherein the pacing output circuit controls delivery of pacingpulses between the first and second left ventricular electrodes and theconductive housing.
 40. An apparatus, comprising: a first lead, wherethe first lead includes a first right ventricular pacing/sensingelectrode at a distal end of the first lead and a first rightventricular defibrillation coil electrode, where both electrodes areadapted to be positioned in a right ventricular region; an implantablepulse generator, where the first lead is releasably coupled to theimplantable pulse generator and where the first right ventricularpacing/sensing electrode and the first right ventricular defibrillationcoil electrode are coupled to control circuitry within the implantablepulse generator, and wherein the control circuitry includes a pacingoutput circuit that controls delivery of pacing pulses from the firstright ventricular defibrillation coil electrode to the first rightventricular pacing/sensing electrode in the right ventricular region.41. A method, comprising: programming pacing pulses vector between atleast one of a first left ventricular electrode and a second leftventricular electrode in a left ventricular region, and a firstsupraventricular electrode in a right atrial region; and delivering apacing pulse according to the programmed pacing pulse vector between atleast one of the first left ventricular electrode and the second leftventricular electrode, and the first supraventricular electrode.
 42. Themethod of claim 41, including programming sensing vectors between atleast one of the first left ventricular electrode and the second leftventricular electrode and the first supraventricular electrode, andsensing a cardiac signal between at least one of the first leftventricular electrode and the second left ventricular electrode, and thefirst supraventricular electrode according to the programmed sensingvector.
 43. The method of claim 41, including programming pacing pulsesvector between at least one of the first left ventricular electrode andthe second left ventricular electrode and a conductive housing of animplantable pulse generator, and where delivering the pacing pulseincludes delivering the pacing pulse between at least one of the leftventricular electrode and the right ventricular electrode, and thehousing according to the programmed pacing pulse vector.
 44. The methodof claim 41, wherein programming pacing pulses vector includesprogramming a pacing pulse vector between at least one of the first leftventricular electrode and the second left ventricular electrode and afirst right ventricular electrode in a right ventricular region; anddelivering a pacing pulse according to the programmed pacing pulsevector between at least one of the first left ventricular electrode andthe second left ventricular electrode, and the first right ventricularelectrode.
 45. The method of claim 44, wherein delivering the pacingpulse includes delivering the pacing pulse from the first and secondleft ventricular electrodes in common to the first right ventricularelectrode.
 46. The method of claim 44, wherein delivering the pacingpulse includes delivering the pacing pulse between the first leftventricular electrode and the second left ventricular electrode and thefirst right ventricular electrode and a housing of an implantable pulsegenerator, where the first and second left ventricular electrodes arecommon and the first right ventricular electrode and the housing arecommon.
 47. The method of claim 41, where programming pacing pulsesvector includes programming the pacing pulse vector between at least oneof the first left ventricular electrode, the second left ventricularelectrode and a third left ventricular electrode in the left ventricularregion, and the first supraventricular electrode in a right atrialregion; and delivering the pacing pulse according to the programmedpacing pulse vector between at least one of the first left ventricularelectrode, the second left ventricular electrode, the third leftventricular electrode and the first supraventricular electrode.
 48. Amethod, comprising: programming pacing pulses vector between at leastone of a first left ventricular electrode and a second left ventricularelectrode in a left ventricular region, and a right ventricularelectrode in a right ventricular region; and delivering a pacing pulseaccording to the programmed pacing pulse vector between at least one ofthe first left ventricular electrode and the second left ventricularelectrode, and the right ventricular electrode.
 49. The method of claim48, including programming sensing vectors between at least one of thefirst left ventricular electrode and the second left ventricularelectrode, and the right ventricular electrode, and sensing a cardiacsignal between at least one of the first left ventricular electrode andthe second left ventricular electrode, and the right ventricularelectrode according to the programmed sensing vector.
 50. The method ofclaim 48, including programming pacing pulses vector between at leastone of the first left ventricular electrode and the second leftventricular electrode, and a conductive housing of an implantable pulsegenerator, and where delivering the pacing pulse includes delivering thepacing pulse between at least one of the left ventricular electrode andthe right ventricular electrode, and the housing according to theprogrammed pacing pulse vector.
 51. The method of claim 48, whereinprogramming pacing pulses vector includes programming a pacing pulsevector between at least one of the first left ventricular electrode andthe second left ventricular electrode, and a supraventricular electrodein a right atrial region; and delivering a pacing pulse according to theprogrammed pacing pulse vector between at least one of the first leftventricular electrode and the second left ventricular electrode, and thesupraventricular electrode.
 52. The method of claim 51, whereindelivering the pacing pulse includes delivering the pacing pulse betweenthe first and second left ventricular electrodes in common to thesupraventricular electrode.
 53. The method of claim 51, whereindelivering the pacing pulse includes delivering the pacing pulse betweenthe first left ventricular electrode and the second left ventricularelectrode and the supraventricular electrode and a housing of animplantable pulse generator, where the first and second left ventricularelectrodes are common and the supraventricular electrode and the housingare common.
 54. The method of claim 48, where programming pacing pulsesvector includes programming the pacing pulse vector between at least oneof the first left ventricular electrode, the second left ventricularelectrode and a third left ventricular electrode in the left ventricularregion, and the first supraventricular electrode in a right atrialregion; and delivering the pacing pulse according to the programmedpacing pulse vector between at least one of the first left ventricularelectrode, the second left ventricular electrode, the third leftventricular electrode and the right ventricular electrode.
 55. A method,comprising: delivering a pacing level pulse from a first ventriculardefibrillation electrode as a cathode to a first ventricularpacing/sensing electrode as an anode.
 56. The method of claim 55,including positioning the first ventricular defibrillation electrode ina right ventricular region, and the first pacing/sensing electrode in anapex of the right ventricular region.